Savings with upgraded performance through improved activated sludge denitrification in the combined activated sludge–biofilter system of the Southpest Wastewater Treatment Plant

Abstract

The purpose of the experiments was to increase the rate of activated sludge denitrification in the combined biological treatment system of the Southpest Wastewater Treatment Plant in order to gain savings in cost and energy and improve process efficiency. Initial profile measurements revealed excess denitrification capacity of the preclarified wastewater. As a consequence, flow of nitrification filter effluent recirculated to the anoxic activated sludge basins was increased from 23,000 m3 d(-1) to 42,288 m3 d(-1) at an average preclarified influent flow of 64,843 m3 d(-1), Both simulation studies and microbiological investigations suggested that activated sludge nitrification, achieved despite the low SRT (2-3 days), was initiated by the backseeding from the nitrification filters and facilitated by the decreased oxygen demand of the influent organics used for denitrification. With the improved activated sludge denitrification, methanol demand could be decreased to about half of the initial value. With the increased efficiency of the activated sludge pre-denitrification, plant effluent COD levels decreased from 40-70 mg l(-1) to < 30-45 mg l(-1) due to the decreased likelihood of methanol overdosing in the denitrification filter.

Performance Evaluation of a Pilot-Scale Aerobic Granular Sludge Integrated with Gravity-Driven Membrane System Treating Domestic Wastewater

“…The denitrification process in the AeMBR or CAS is highly dependent on the recycle flow from the oxic (nitrification) to the anoxic tank and sometimes requires the supply of external carbon. External carbon dosage is costly and can lead to elevated BOD concentrations in the effluent when overdosed . One of the main advantages of the AGS process is that the biological nitrogen removal processes are not separated in different oxic and anoxic tanks.…”

Pilot-scale verification of efficient nitrifier backseeding in a combined activated sludge-biofilm system

“…supported by full-scale experiments aiming increased denitrification efficiency at the Southpest WWTP (Jobbágy et al [11]). …”

“…Simulation studies with this model revealed that efficient backseeding may considerably improve performance by enhancing nitrification ability of the activated sludge unit, thereby facilitating considerable savings in both methanol and aeration costs. Full-scale results verified the applicability of the model, but long-term, efficient nitrification could not be achieved in the full-scale activated sludge unit although the enhanced activated sludge denitrification decreased the oxygen demand of carbon removal (Jobbágy et al [11]). No direct investigation of possibly facilitating efficient backseeding through increased activated sludge aeration had been carried out.…”

“…Activated sludge denitrification with the carbon source of the influent wastewater may result in savings in the external carbon source required as well as in the oxygen demand and lower effluent COD and nitrate levels can be achievable (Jobbágy et al [11]). …”